It is known to the art the difficulties to treat a bone fracture near a joint. Prior known methods and arrangements in this context have not safeguarded all necessary requirements when it comes to accuracy in fixation of bone parts using methods including a cutting sequence. In unfortunate circumstances a poor accuracy may later on affect the healing process as well as the rigidity of the bone parts when a normal healing period or process has passed, with possible further convalescence or re-operation required.
The present invention is described in connection with fracture disorders related to the wrist, particularly those that result in misalignment between a first part of a bone named radius, and another part of a bone named ulna, causing interference, for instance in the sigmoid notch of the wrist.
The invention is not restricted to this application and can be used when treating bones of the elbow, knee, and ankle. These applications may require a change in the shape of the inventive device related to each specific application, but the same principles are used irrespective of the site of the misalignment. However, the major use of the invention is expected to be for treating deformities and disorders of the distal radial ulnar joint.
The treatment of joint misalignment has been a problem because of the frequency of the injury disorders and the difficulties in correct treating.
The object of the invention is to restore an alignment between the radius and the ulna in order to prevent arthritis and to relieve pain as well as to minimize the impaction and pressure between the ulna and the carpus of the wrist. Misalignment between the radius and the ulna can result from injury or idiopathic conditions where the ulna is excessively long in relationship to the radius. Injuries that result in a fracture or dislocation of the radius can end up producing a radius that is too short in relationship to the ulna that allows the prominent distal end of the ulna to impact and apply excessive pressure to the carpus of the wrist, the triangular fibre cartilage that covers the distal end of the ulna.
There are essentially five general groups of options available for treatment of misalignment between the radius and the ulna or the joint referred to as the distal radius ulnar joint, these are:                (1) Complete excision of the distal end of the ulna,        (2) Partial excision of the distal end of the ulna,        (3) Excision of the ulna and replacement with a prosthetic joint,        (4) Fusion between the radius and the ulna with excision of a segment proximal to the fused joint to create a false joint, and        (5) Shortening of the ulna.        
Excision of the distal end of the ulna can relieve the pain resulting from arthritic joints or increased pressure and impaction between the ends of the ulna and the carpus, but it results in an unstable joint, which frequently increases instability of the ulna that produces additional symptoms for which no treatment options can subsequently restore the action of the destroyed joint.
Partial excision of the end of the ulna strives to relieve the pressure between the ulna and the carpus while still allowing some portion of the joint to reserve a normal relationship and rotation between the radius and the ulna. Unfortunately, many patients experience significant pain because the normal cartilage and joint contacting between the triangular cartilage and ulna have been removed.
Removal of the distal ulna and replacement with a prosthetic joint allows for correction of the length of the ulna at the time of joint replacement, and may be satisfactory in older patients, but in younger, active patients the action between the metal surface of the ulna will cause destruction of the normal cartilage of the radius, with which it articulates. The loss of cartilage from the radius can result in recurrence of pain in the patient.
Arthrodesis of the joint and the creation of a false joint proximalis by removing a segment of bone have been referred to as the Sauve-Kapandji procedure. Although this can relieve symptoms of pain because the joint is fused, the rate of arthrodesis is unreliable and the false joint below can cause instability, clicking, and pain that is very difficult to treat because the resected bone can cause instability and pain.
Shortening osteotomies have been developed to preserve the normal joint and restore the correct alignment between the radius and the ulna. However, a failure to properly coat the bone surfaces of the osteotomy can result in delayed healing or a non-union.
A few major techniques have been developed, which include both a transverse osteotomy, as well as an oblique osteotomy. A comparison study demonstrated that transverse osteotomies require 21 weeks to heal while the oblique osteotomies healed in 11 weeks. (Reference Rayhack J M, Gasser S I, Latti L L, Ouellette E A, and Maline E L: Precision oblique osteotomy for shortening of the ulna, JHS 1993, Vol. 18A: 908-18). Oblique osteotomies can be performed either with or without the use of a lag screw through the plate and across the osteotomy to improve the compression. Providing a lag screw across the osteotomy site substantially improves the compression of the site and enhances bone healing. It is difficult to compress the bones, as there are other tissues attached to the bone that prevent the compression.
Few major techniques for providing the bone compression involve making an unguided or free hand bone cut followed by the application of a plate. This requires multiple assistance to guide the bone ends together while the osteotomy is performed.
The other method is to use a cutting guide and then apply a device with a compression screw system to bring the bone ends together. The freehand technique has a high margin of error and if the bone surfaces are not cut parallel, there is poor coaptation of the bones and a high rate of non-union. Also, the amount of bone removed is very imprecise. The technique that uses a cutting guide with the compression screw requires that the cutting guide be removed before applying the final plate implant. This technique will result in loss of alignment once the cutting guide is removed, as the final implant in the bone being cut cannot be visualized, and if the cutting guide provides any errors because of the way the device is assembled, significant problems may occur. The cutting guide from this device blocks and prevents the surgeon or physician from viewing the structures around the bone and injury to the bony structures by the saw can occur. Finally, this device uses two separate screws for compression of the osteotomy that cannot be compressed at the same time. As a result, misalignment between the bone surfaces often occurs.
Contrary hereto, according to the invention, a method of oblique osteotomy for the bone shortening is described, which allows for lag screw compression through the plate and can be performed while the plate is already attached to the bone, thus preventing loss of alignment.
The osteotomy can be directly visualized while the plate is in place in order to make sure that the physician can ensure that the cuts are accurate and that all soft tissues around the bone can be protected. A single central screw compression is all that is needed between the bone ends created to optimise the healing of the osteotomy.